From e4bc6522d53b7b8eb02cfac35fd18275fd86269d Mon Sep 17 00:00:00 2001 From: Li Wang Date: Tue, 30 Oct 2012 19:52:40 +0800 Subject: [PATCH] eCryptfs: Avoid unnecessary disk read and data decryption during writing ecryptfs_write_begin grabs a page from page cache for writing. If the page contains invalid data, or data older than the counterpart on the disk, eCryptfs will read out the corresponing data from the disk into the page, decrypt them, then perform writing. However, for this page, if the length of the data to be written into is equal to page size, that means the whole page of data will be overwritten, in which case, it does not matter whatever the data were before, it is beneficial to perform writing directly rather than bothering to read and decrypt first. With this optimization, according to our test on a machine with Intel Core 2 Duo processor, iozone 'write' operation on an existing file with write size being multiple of page size will enjoy a steady 3x speedup. Signed-off-by: Li Wang Signed-off-by: Yunchuan Wen Signed-off-by: Tyler Hicks --- fs/ecryptfs/mmap.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c index bd1d57f98f74..564a1fa34b99 100644 --- a/fs/ecryptfs/mmap.c +++ b/fs/ecryptfs/mmap.c @@ -338,7 +338,8 @@ static int ecryptfs_write_begin(struct file *file, if (prev_page_end_size >= i_size_read(page->mapping->host)) { zero_user(page, 0, PAGE_CACHE_SIZE); - } else { + SetPageUptodate(page); + } else if (len < PAGE_CACHE_SIZE) { rc = ecryptfs_decrypt_page(page); if (rc) { printk(KERN_ERR "%s: Error decrypting " @@ -348,8 +349,8 @@ static int ecryptfs_write_begin(struct file *file, ClearPageUptodate(page); goto out; } + SetPageUptodate(page); } - SetPageUptodate(page); } } /* If creating a page or more of holes, zero them out via truncate. @@ -499,6 +500,13 @@ static int ecryptfs_write_end(struct file *file, } goto out; } + if (!PageUptodate(page)) { + if (copied < PAGE_CACHE_SIZE) { + rc = 0; + goto out; + } + SetPageUptodate(page); + } /* Fills in zeros if 'to' goes beyond inode size */ rc = fill_zeros_to_end_of_page(page, to); if (rc) {